Please Help...huge Crack On Fondant!!

I made am making a 3 tiered cake for a baby shower. I layed my fondant last night and noticed that one of the cakes had a huge air bubble....I puntured it and tried smoothing it out but then it began to crack. I sliced right trough the crack and smoothedi t out, I figured I could just make this the back of the cake. I am putting stars also so I figured I could cover some of the damage. When I woke this morning that part of the fondant was detached from the cake What do I do now to fix this ? It doesnt stick to the cake anymore! What did I do wrong to cause this and how can I prevent this from happening in the future?